1. Field of the Invention
The present invention relates to an inverted F antenna (PIFA). More particularly, the present invention relates to a multi-band PIFA for a thin communication apparatus.
2. Description of Related Art
Design features of handheld 3G (3rd generation) communication apparatuses such as cell phones have a general trend of lightness, slimness, shortness and smallness. Therefore, a conventional antenna design has become inapplicable for accomplishment of above features. To design a broadband antenna, limitation of height thereof is a challenge.
There are two general methods for designing the antenna for wireless communication products on the market. One is a PIFA, which has a commonly used antenna structure, which includes a main body, a feed point and a ground point, by which a plurality of required resonant frequencies may be obtained via two current paths with different lengths. Another one is a so-called monopole antenna, which has a clearance region to avoid interference of antenna effect occurred due to excessive closed electronic components during operation, such that the antenna may be operated under an optimal bandwidth.
As to the PIFA, limitation of the height (a spacing distance between the main body and a circuit substrate) is a great challenge. If the PIFA were to be built within a slim, multi-band handheld communication apparatus, the bandwidth thereof may become a great problem. If the monopole antenna is applied in the slim handheld communication apparatus, the circuit substrate is required to provide a complete clearance region for utilization of the antenna, such that size of the apparatus is increased, meanwhile, utilization of such antenna is influenced by excessive specific absorption ratio (SAR) of human body and phantom.